The effects of MgO, Na2O and SO3 on industrial clinkering process: phase composition, polymorphism, microstructure and hydration, using a multidisciplinary approach

Preprint publicado en: Materials Characterization Volume 155, September 2019, 109809The present investigation deals with how minor elements (their oxides: MgO, Na2O and SO3) in industrial kiln feeds affect (i) chemical reactions upon clinkering, (ii) resulting phase composition and microstructure of clinker, (iii) hydration process during cement production. Our results show that all these points are remarkably sensitive to the combination and interference effects between the minor chemical species mentioned above. Upon clinkering, all the industrial raw meals here used exhibit the same formation temperature and amount of liquid phase. Minor elements are preferentially hosted by secondary phases, such as periclase. Conversely, the growth rate of the main clinker phases (alite and belite) is significantly affected by the nature and combination of minor oxides. MgO and Na2O give a very fast C3S formation rate at T > 1450 K, whereas Na2O and SO3 boost C2S After heating, if SO3 occurs in combination with MgO and/or Na2O, it does not inihibit the C3S crystallisation as expected. Rather, it promotes the stabilisation of M1-C3S, thus indirectly influencing the aluminate content, too. MgO increseases the C3S amount and promotes the stabilisation of M3-C3S, when it is in combination with Na2O. Na2O seems to be mainly hosted by calcium aluminate structure, but it does not induce the stabilisation of the orhtorhombic polymorph, as supposed to occur. Such features play a key role in predicting the physicalmechanical performance of a final cement (i.e. rate of hydration and hardening) when used as a bulding material.The present study has been partly funded by the project PRIN 2017 (2017L83S77), of the Italian Ministry for Education, University and Research (MIUR)

INCREASING THE DIMENSIONAL STABILITY OF CAO-FEOX-AL2O3-SIO2 ALKALI-ACTIVATED MATERIALS: ON THE SWELLING POTENTIAL OF CALCIUM OXIDE-RICH ADMIXTURES

Advanced thermochemical conversion processes are emerging technologies for materials\u2019 recovery and energetic conversion of wastes. During these processes, a (semi-)vitreous material is also produced, and as these technologies get closer to maturity and full-scale implementation, significant volumes of these secondary outputs are expected to be generated. The production of building materials through the alkali activation of such residues is often identified as a possible large-scale valorization route, but the high susceptibility of alkali-activated materials (AAM) to shrinkage limits their attractiveness to the construction sector. Aiming to mitigate such a phenomenon, an experimental study was conducted investigating the effect of calcium oxide-rich admixtures on the dimensional stability of CaO-FeOx-Al2O3-SiO2 AAMs. This work describes the impacts of such admixtures on autogenous and drying shrinkage, porosity, microstructure, and mineralogy on AAMs. Drying shrinkage was identified as the governing mechanism affecting AAM volumetric stability, whereas autogenous shrinkage was less significant. The reference pastes presented the highest drying shrinkage, while increasing the dosage of shrinkage reducing agent (SRA) was found to reduce drying shrinkage up to 63%. The reduction of drying shrinkage was proportional to SRA content; however, elevated dosages of such admixture were found to be detrimental for AAM microstructure. On the other hand, small dosages of calcium oxide-rich admixtures did not induce significant changes in the samples\u2019 mineralogical evolution but promoted the formation of denser and less fractured microstructures. The results presented here show that calcium oxide-rich admixtures can be used to increase AAM\u2019s volumetric stability and an optimal dosage is prescribed

The new phylogenesis of the genus Mycobacterium

Abstract Phylogenetic knowledge of the genus Mycobacterium is based on comparative analysis of their genetic sequences. The 16S rRNA has remained for many years the only target of such analyses, but in the last few years, other housekeeping genes have been investigated and the phylogeny based on their concatenated sequences become a standard. It is now clear that the robustness of the phylogenetic analysis is strictly related to the size of the genomic target used. Whole genome sequencing (WGS) is nowadays becoming widely accessible and comparatively cheap. It was decided, therefore, to use this approach to reconstruct the ultimate phylogeny of the genus Mycobacterium . Over 50 types of strains of the same number of species of Mycobacterium were sequenced using the Illumina HiSeq platform. The majority of the strains of which the whole sequence was already available in GenBank were excluded from this panel with the aim of maximizing the number of the species with genome available. Following assembling and annotation with proper software, the phylogenetic analysis was conducted with PhyloPhlAn and the pan-genome analysis pipeline. The phylogenetic three which emerged was characterized by a clear-cut distinction of slowly and rapidly growing species with the latter being more ancestral. The species of the Mycobacterium terrae complex occupied an intermediate position between rapid and slow growers. Most of the species revealed clearly related and occupied specific phylogenetic branches. Thanks to the WGS technology, the genus Mycobacterium is finally approaching its definitive location

Nox2-deficient Tregs improve heart transplant outcomes via their increased graft recruitment and enhanced potency.

Nox2 is a ROS-generating enzyme, deficiency of which increases suppression by Tregs in vitro and in an in vivo model of cardiac remodelling. Since Tregs have emerged as a candidate therapy in autoimmunity and transplantation, we hypothesised that Nox2 deficiency in Tregs in recipient mice may improve outcomes in a heart transplant model. A novel B6129 mouse model with Treg-targeted Nox2 deletion (Nox2fl/flFoxP3Cre+) was generated and transplanted with hearts from CB6F1 donors. As compared to littermate controls, Nox2fl/flFoxP3Cre+ mice had lower plasma levels of alloantibodies and troponin-I, reduced levels of IFN-γ in heart allograft homogenates and diminished cardiomyocyte necrosis and allograft fibrosis. Single cell analyses of allografts revealed higher absolute numbers of Tregs and lower CD8+ T cell infiltration in Nox2-deficient recipients compared to Nox2-replete mice. Mechanistically, in addition to a greater suppression of CD8+CD25- T effector cell proliferation and IFN-γ production, Nox2-deficient Tregs expressed higher levels of CCR4 and CCR8, driving cell migration to allografts; this was associated with increased expression of miR214-3p. These data indicate that Nox2 deletion in Tregs enhances their suppressive ability and migration to heart allografts. Therefore, Nox2 inhibition in Tregs may be a useful approach to improve their therapeutic efficacy

Building essential biodiversity variables (EBVs) of species distribution and abundance at a global scale

Much biodiversity data is collected worldwide, but it remains challenging to assemble the scattered knowledge for assessing biodiversity status and trends. The concept of Essential Biodiversity Variables (EBVs) was introduced to structure biodiversity monitoring globally, and to harmonize and standardize biodiversity data from disparate sources to capture a minimum set of critical variables required to study, report and manage biodiversity change. Here, we assess the challenges of a 'Big Data' approach to building global EBV data products across taxa and spatiotemporal scales, focusing on species distribution and abundance. The majority of currently available data on species distributions derives from incidentally reported observations or from surveys where presence-only or presence-absence data are sampled repeatedly with standardized protocols. Most abundance data come from opportunistic population counts or from population time series using standardized protocols (e.g. repeated surveys of the same population from single or multiple sites). Enormous complexity exists in integrating these heterogeneous, multi-source data sets across space, time, taxa and different sampling methods. Integration of such data into global EBV data products requires correcting biases introduced by imperfect detection and varying sampling effort, dealing with different spatial resolution and extents, harmonizing measurement units from different data sources or sampling methods, applying statistical tools and models for spatial inter- or extrapolation, and quantifying sources of uncertainty and errors in data and models. To support the development of EBVs by the Group on Earth Observations Biodiversity Observation Network (GEO BON), we identify 11 key workflow steps that will operationalize the process of building EBV data products within and across research infrastructures worldwide. These workflow steps take multiple sequential activities into account, including identification and aggregation of various raw data sources, data quality control, taxonomic name matching and statistical modelling of integrated data. We illustrate these steps with concrete examples from existing citizen science and professional monitoring projects, including eBird, the Tropical Ecology Assessment and Monitoring network, the Living Planet Index and the Baltic Sea zooplankton monitoring. The identified workflow steps are applicable to both terrestrial and aquatic systems and a broad range of spatial, temporal and taxonomic scales. They depend on clear, findable and accessible metadata, and we provide an overview of current data and metadata standards. Several challenges remain to be solved for building global EBV data products: (i) developing tools and models for combining heterogeneous, multi-source data sets and filling data gaps in geographic, temporal and taxonomic coverage, (ii) integrating emerging methods and technologies for data collection such as citizen science, sensor networks, DNA-based techniques and satellite remote sensing, (iii) solving major technical issues related to data product structure, data storage, execution of workflows and the production process/cycle as well as approaching technical interoperability among research infrastructures, (iv) allowing semantic interoperability by developing and adopting standards and tools for capturing consistent data and metadata, and (v) ensuring legal interoperability by endorsing open data or data that are free from restrictions on use, modification and sharing. Addressing these challenges is critical for biodiversity research and for assessing progress towards conservation policy targets and sustainable development goals

Turning toxic industrial waste to something useful : thermal treatments of Cr-bearing sludges from tanneries for inertization and recycling

Leather treatment in the tanneries may employ high dosages of chromium. Beside the smell in the immediate neighbourhood, the production of great quantities of Cr-rich waste waters makes this type of industrial activity as one of the worst for the environment. Tannery waste waters and their solid sediment (sludge) may be variably treated before being disposed: more frequently lime is added in order to oxidate proteins; attempts are done to recover tanning Cr. Only one tannery in Scandinavia owns a pyrolysis plant where Cr is recovered as Cr-Fe alloy and a safely disposable vitrified and unleachable slag is produced. We started a series of thermal treatments on waste sludge from tanneries. Our aim is to turn the inorganic part of the sludge into a harmless ceramic slag. Then this material can possibly be recycled, e.g. in road construction or in concrete. The composition of the inorganic fraction of the tannery sludge includes variable amounts of Ca (depending on treatment with lime), Na, Cr and Fe (both in the % range), with subordinate Mg, Mn, Al, P, Ti, Zn, etc.. We prepared series of mixtures of variably treated waste with natural additives such as kaolinitic clay, magnesite, silica (quartz) and in some cases alumina. We planned to induce crystallization of chemically stable Ca-Al-Mg silicates and oxides immobilizing Cr, Fe and the other metal components. The ratio of waste to additives was always between 1:1 and 3:2. We used sludge in four different conditions: sludge with or without lime treatment and with simple dehydration at 120\ub0C or heated at 550\ub0C (decomposition of organics). The mixed bulk compositions were planned to correspond to three different mineral assemblages containing Ca-silicates and spinel: gehlenite + spinel, diopside + spinel and anorthite + spinel. The mixtures were pressed in cylindric pellets and heated in a vertical furnace up to 1300\ub0C in several runs according to different thermal schemes. The thermal schemes comprise (a) rapid heating, (b) dwell at the maximum temperature variable between one to four hours and (c) slow cooling (to prevent glass formation).The runs lasted less than 1 day in order to simulate rapid industrial-scale treatment, and at first they were done in moderately reducing atmosphere determined by flux of a mixture of air and CO2 (50 cc/min each) to prevent oxidation of Cr. The run products were characterized for their phase assemblages by x-ray powder diffraction techniques, by scanning electron microscope (SEM) equipped with EDS for chemical microanalysis and by x-ray data refinement methods (Rietveld). The run products are characterized by dominant granular texture, fine to very fine grain size, high porosity and disequilibrium textures due to short residence time at high temperature. The phase assemblages obtained contain a range of Ca-bearing silicates such as melilites (gehlenite-\ue5kermanite), diopside-type pyroxene, anorthite and grossular-type Ca-garnet.They occur as fine to coarse grains and/or reaction rims around newly-formed phases or unreacted/refractory grains. Unreacted and refractory phases are represented by quartz, periclase from decomposition of magnesite or corundum (when added).The porous matrix to the coarser grains may also include aggregates of very fine-grained Cr-Fe(-Zn)-rich Mg-spinels, undetermined lamellar Fe-Cr phases and phosphates. Occasionally disseminated micro-pellets of Cr-Fe-Ti-Al alloys occur. The best results in terms of textures and phase assemblages significant for effective inertization are those for bulk compositions involving sludges pre-heated at 550\ub0C (i.e. without organic component) and with longer residence time (e.g. 2 to 4 hours) at high temperature: better degree of crystallization, coarser textures, greater abundance of stable phases and minimal gaseous emissions

THE EFFECT OF CaO-RICH ADMIXTURES ON CONTROLLING DRYING SHRINKAGE OF ALKALI ACTIVATED MATERIALS

Alkali-activated materials (AAM) are emerging in the construction sector by providing an opportunity to up-stream several industrial by-products. One of the main technical challenges regarding these by-product-based innovative materials is to overcome their tendency to suffer severe drying shrinkage. In this work, the feasibility of using CaO-based admixtures to mitigate drying shrinkage phenomena was investigated and its effects on fresh pastes and hardened specimens’ properties are described. The obtained results showed that increasing CaO-rich admixtures dosage up to 3.0 wt% has a beneficial impact on AAMs volumetric stability. A maximum drying shrinkage reduction of 62.1% was achieved and samples with low open porosity and considerable flexural (up to 7 MPa) and compressive strength (up to 116 MPa) were produced. Notwithstanding, elevated CaO dosages induced detrimental modifications on pastes workability suggesting a dosage threshold of 2.0 wt%. At this dosage, strength development and a reasonable setting time were maintained while linear deformation reduced up to 40%. Reducing alkali-activated materials susceptibility to shrinkage is expected to increase their attractiveness for large-scale applications, and by doing so, will contribute to the valorisation of industrial by-products, facilitating the transition towards a circular economy, while suppressing the usage of virgin raw materials

Reaction kinetics and structural analysis of alkali activated Fe-Si-Ca rich materials

status: publishe

Increasing the dimensional stability of CaO-FeOx-Al₂O₃-SiO₂ alkali-activated materials: On the swelling potential of calcium oxide-rich admixtures

Advanced thermochemical conversion processes are emerging technologies for materials’ recovery and energetic conversion of wastes. During these processes, a (semi-)vitreous material is also produced, and as these technologies get closer to maturity and full-scale implementation, significant volumes of these secondary outputs are expected to be generated. The production of building materials through the alkali activation of such residues is often identified as a possible large-scale valorization route, but the high susceptibility of alkali-activated materials (AAM) to shrinkage limits their attractiveness to the construction sector. Aiming to mitigate such a phenomenon, an experimental study was conducted investigating the effect of calcium oxide-rich admixtures on the dimensional stability of CaO-FeOx-Al2O3-SiO2 AAMs. This work describes the impacts of such admixtures on autogenous and drying shrinkage, porosity, microstructure, and mineralogy on AAMs. Drying shrinkage was identified as the governing mechanism affecting AAM volumetric stability, whereas autogenous shrinkage was less significant. The reference pastes presented the highest drying shrinkage, while increasing the dosage of shrinkage reducing agent (SRA) was found to reduce drying shrinkage up to 63%. The reduction of drying shrinkage was proportional to SRA content; however, elevated dosages of such admixture were found to be detrimental for AAM microstructure. On the other hand, small dosages of calcium oxide-rich admixtures did not induce significant changes in the samples’ mineralogical evolution but promoted the formation of denser and less fractured microstructures. The results presented here show that calcium oxide-rich admixtures can be used to increase AAM’s volumetric stability and an optimal dosage is prescribed.status: publishe